The Ginkgo biloba tree mentioned in the Chinese Materia Medica 5000 years ago (Deng, Q. Drug Use Perspective 1988, 1, 57-58) has gained wide interest for its biological activities, especially in the treatment of memory related afflictions. Standardized extract EGb761 (Drieu, K.; Jaggy, H. in Ginkgo biloba; van Beek, T. A., Ed.; Harwood Academic Publishers: Amsterdam, 2000; Vol. 12, pp 267-277) from G. biloba leaves is a complex mixture containing flavonoids (22-24%) and terpene trilactones (TTL, 5-7%), and is one of the best selling herbal medicines (Schmid, W. Nature (London) 1997, 386, 755). The structures of ginkgolides A, B, and C were determined in 1967 (FIG. 1), (Nakanishi, K: Pure Appl. Chem. 1967, 14, 89-113; Okabe, K.; Yamada, K.; Yamamura, S.; Takada, S. J. Chem. Soc. C 1967, 2201-2206) while those of ginkgolide J (Weinges, K.; Hepp, M.; Jaggy, H. Liebigs Ann. Chem. 1987, 521-526) and bilobalide (Nakanishi, K.; Habaguchi, K.; Nakadaira, Y.; Woods, M. C.; Maruyama, M.; Major, R. T.; Alauddin, M.; Patel, A. R.; Weinges, K.; Bahr, W. J. Am. Chem. Soc. 1971, 93, 3544-3546) were elucidated later. Flavonoids and TTLs are believed to be associated with most of the pharmacological properties of G. biloba extracts. While flavonoids can be obtained from many other plants, ginkgolides and bilobalide are unique components of G. biloba extracts. They have attracted scientists to investigate the biological activity and putative link of these compounds to pharmacological activities of EGb761, particularly those related to neuromodulation (long term potentiation, cognitive symptoms of dementia) (MacLennan, K. M.; Darlington, C. L.; Smith, P. F. Progress in Neurobiology (Oxford, United Kingdom) 2002, 67, 235-257). Ginkgolides are well known for their platelet activating factor antagonistic activity (Braquet, P. Drugs of the Future 1987, 12, 643-699) and recently also for the selective inhibition of glycine receptors(Kondratskaya, E. L.; Krishtal, O. A. Neurophysiology (Translation of Neirofiziologiya) 2002, 34, 155-157). Although bilobalide lacks these activities its neuroprotective properties have been reported(Zhou, L. J.; Zhu, X. Z. J. Pharmacol. Exp. Ther. 2000, 293, 982-988; Janssens, D.; Remacle, J.; Drieu, K.; Michiels, C. Biochem. Pharmacol. 1999, 58, 109-119; Chandrasekaran, K.; Mahrabian, Z.; Spinnewyn, B.; Drieu, K.; Fiskum, G. Brain Research 2001, 922, 282-292). Recently, methods for the extraction of TTLs with organic solvents(PCT International Application No. WO 02/083158, published Oct. 24, 2002 (Teng, B. P.)), water (Lichtblau, D.; Berger, J. M.; Nakanishi, K. Journal of Natural Products 2002, 65, 1501-1504; U.S. Pat. No. 6,590,109, issued Jul. 8, 2003 to Lichtblau, et al.)), pressurized water (U.S. Pat. No. 6,524,628, issued Feb. 25, 2003 to Wai, et al.) or supercritical fluids (Choi, Y. H.; Kim, J.; Yoo, K. P. Chromatographia 2002, 56, 753-757; van Beek, T. A.; Taylor, L. T. Phytochemical Analysis 1996, 7, 185-191) have been developed. The individual terpene components can be separated from these enriched extracts by a 10-15 step fractional recrystalization (Nakanishi, K. Pure Appl. Chem. 1967, 14, 89-113; Okabe, K.; Yamada, K.; Yamamura, S.; Takada, S. J. Chem. Soc. C 1967, 2201-2206; Zhao, J.; Muhammad, I.; Dunbar, D. C.; Khan, I. A.; Fischer, N. H.; Fronczek, F. R. Acta Crystallagraphica, Section C.: Crystal Structure Communications 2002, C58, o195-o198; Dupont, L.; Dideberg, O.; Germain, G.; Braquet, P. Acta Cryst. 1986, C42, 1759-1762; Sbit, M.; Dupont, L.; Dideberg, O.; Braquet, P. Acta Cryst. 1987, C43, 2377-2381) repeated column chromatography (Weinges, K.; Bahr, W. Liebigs Ann. Chem. 1972, 759, 158-172), reversed-phase HPLC (Wada, K.; Sasaki, K.; Miura, K.; Yagi, M.; Kubota, Y.; Matsumoto, T.; Haga, M. Biological and Pharmaceutical Bulletin 1993, 16, 210-212; Lobstein-Guth, A.; Briancon-Scheid, F.; Anton, R. Journal of Chromatography 1983, 267, 431-438; Camponovo, F. F.; Wolfender, J. L.; Maillard, M. P.; Potterat, O.; Hostettmann, K. Phytochemical Analysis 1995, 6, 141-148, chromatography system with sephadex LH-20 (Teng, B. P. In Ginkgolides—Chemistry, Biology, Pharmacology; Braquet, P., Ed.; J. R. Prous Science Publishers, S. A., 1988, pp 37-42) or less problematically by chromatography on NaOAc impregnated silica gel (van Beek, T. A.; Lelyveld, G. P. J. Nat. Prod. 1997, 60, 735-738).
In contrast to the large number of methods in which the separation procedure is rather complicated or the individual terpene trilactones can only be obtained in low purity and/or low quality, described herein are simple and efficient separation methods for the separation of five terpene trilactones from G. biloba extract by a combination of benzylation, chromatography, and hydrogenolysis or a combination of extraction, chromatography and crystallization. Of particular importance for large-scale isolation of ginkgolides as phytopharmaceuticals, the described method enables separation without resorting to preparative reversed-phase HPLC or other expensive procedures.